Magnetic latching crossbar switch



p 1953 D. D. SIMMONS ETAL 3,102,931

' MAGNETIC LATCHING CROSSBAR SWITCH Filed Feb. 3, 1961 ROCKWELL HARD/v5.55 58-60 a CARBON 25% .smcon .507- MANGANESE 1.20 TUNGsTEN .507- CHROMIIJM .507- VANADIUM 20% OUTER wmoma (WOUND CLDCKWIQE) INVENTOR5 INNER wmoma (woum: COUNTER-CLOGKWISE) Doraegflflmnzonfi,

United States Patent 3,102,931 MAGNETIC LATHING CRQSSBAR SWITH Dorsey D. Simmons and Carl Gunner Svala, Galron, Qhio, assignors to North Electric Company, Gallon, Ohio, a corporation of Ohio Filed Feb. 3, 1961, Ser. No. 86,940 Claims. (Cl. 1 .79-27.54)

.The present invention relates to a magnetic latching crossbar switch for use in automatic telephone systems, data transmission systems and other similar types of switching systems.

It has long been apparent that the provision of efiicient, reliable service in an automatic telephone system is basically dependent upon the provision of switching equipment which is capable of extending connections in an efficient, expeditious and reliable manner. With the more recent development of additional arts and fields involving data transmission (computers, machine control equipment and the like), the need for switches of increased reliability and good quality transmission have become further apparent.

Experience in the different fields has indicated that in many of these applications the so-called crossbar switch appears to be most successful in providing the high degree of service and reliability required in expeditiously establishing paths for both speech and data transmission. Among other reasons the simple setting of one bar magnet and one vertical unit magnet to complete a desired path over the switch in some tens of milliseconds constitutes both an expeditious and reliable type selecting operation. Additional paths may then be established over the same switch, the total number of paths being as large as the number of vertical magnets on the switch, whereby a reduced number of switching units is required to estab-' lish a given number of connections. Further the pressure contacts (which are similar to relay contacts) of the switch operate with an insignificant amount of wear, and the operation of a contact set obviously does not establish path disturbing vibrations ofthe type which are frequently experienced with the well lmowdrotary type selector switches, and increased reliability in operation may therefore be expected.

As a result of these and other advantages, the usefulness and desirability of crossbar switches in establishing speech and data transmission paths has become well known in the field. A novel type crossbar switch has now been discovered which provides even further advantages in itsuse in ,a switching network. That is, a novel crossbar switch has now been provided which includes means operative to latch the operated magnets of a crossbar switch with residual magnetic energy whereby the asso-' ciated contacts controlled by the magnet will be maintained closed subsequent to interruption of the energizing circuit for the magnet. The latched magnet may be restored to interrupt the connection established over its associated contacts, as desired, by coupling a momentary current pulse of given polarity to the latching magnet.

I In the establishment of a connection over an automatic telephone system, as many as ten or twelve hold magnets may be maintained in the operated position. ,It is apparent that in. a large metropolitan exchange in which hundreds of connections are established during the same period of time, the operating current required to maintain such connection is of a substantial order, and the use of magnetic latching magnets will result in a large reduction in the power requirement. Further, the reduction of 3-,lfi-Z33-l Patented Sept. 3, i363 ice In the provision of a crossbar. switch which includes means for maintaining transmission paths without further power drain subsequent to the initial operation thereof, it is important that the operation be both expeditious and reliable. It has been the experience of the field that the use of a mechanical locking device for such purpose is not particularly satisfactory in achieving such manner of operation. It is a specific object of the present inven tion therefore to provide a crossbar switch which includes a novel magnetic latching relay'having operating characteristics of a value to operate'an associated set of con tacts in a crossbar switch responsive to coupling of a pulse of a predetermined value thereto, to maintain the contacts operated subsequent to the termination of the energizing pulse to the latching relay, and to effect the release of the contact sets responsive to the receipt of a. release pulse of a further predetermined value.

In the provision of a crossbar switch includinga magnetic latching type relay which is operative in such mannor a number of difiiculties are encountered. That is, the

range of the load on the magnet will vary with the contact spring assemblies controlled thereby, and further with the nature of the particular switching operation being performed by the crossbar switch magnet. Ratios of 10:1 for maximum and minimum'loads on a magnet are not uncommon in such type switches.

istics of a magnetic latching relay which is operative in such environment is of an extremely demanding and critical'nature, and the provision of a core material of a new and novel magnetic characteristic is essential to the acfcomplishment of a latching relay which is operative in such manner.

It is a further specific object of the present invention, therefore, to provide a magnetic latching relay for use in a crossbar system which has a structure including a magnetic core which is of a material which provides operrating forces of a value sufiicient to effect attraction of the armature associated therewith under the extremely large variation in load conditions experienced in such use; to provide a holding force sufficient to hold the magnet as the energizing circuit is interrupted and to prevent release of the armature during such latching period even with the occurrence of environmental vibrational forces;

and of a value to eifect release of the magnet responsive to receipt of a momentary release pulse of the low values commonly used in such systems.

It is still another object of the invention to provide a novel magnetic latching relay for use in switching systems such as automatic telephone systems, which has a magnetic core comprised of a high carbon steel material having a hardness in the range of 58-60 Rockwell C to provide the required operating and release characteristics necessary for operation with the loads and operating pulses which occur in such type switching system.

These and other objects of the invention will be apof the different vertical groups 12, 14, 16, etc.

parent with reference to the following specification, claims and drawings, in which:

FIGURE 1 is a schematic illustration of the novel crossbar-switch including the component parts for magnetically completing and maintaining a transmission path thereover; 1

FIGURE 2 is a side-elevational view of the novel magnetic latching relay utilized in the crossbar switch of FIGURE 1; and

FIGURE 3 is a schematic perspective view of the coil and windings used in the magnetic latching relay of FIGURE 2.

SPECIFIC DESCRIPTION The novel crossbar switch. 10, as schematically shown in FIGURE 1, consists of a welded steel trame, partially shown at 11, on which are mounted ten vertical groups of contacts, such as the illustrated vertical groups 12, 14, 16, the contacts of each vertical group being arranged horizontal rows or levels, each of which horizontal rows contains two or more contacts, such as illustrated contacts 18, 24); 22, 24; 2'6, 28; etc. 1

Each vertical group, such as 14, includes two or more vertical contact strips, such as 32, 34, which are com- -mon to the vertical row of horizontal contacts 18, 20; 22,, 24; etc., and supported in vertical spaced relation therewith. Each vertical group, such as 14, is further equipped with a vertical electromagnet, such as 36, for controlling operation of an armature such as 38, which is in turn coupled to a vertical hold bar, such as ill, to move same in an arcuate path about a vertical axis.

A contact actuating spring, such as 42, is supported '4 i by the frame 11 in cantilever fashion between the vertical hold bar 40 and one of its associated contact sets such as 13, 20, and locates a U-shaped channel disposed in the path of'movement of the vertical hold bar 40. A

to selector bar 50) from the normal position to two alternate operating positions (which are readily apparent in FIGURE 1) to thereby til-t the horizontal bar upwardly or downwardly in an arcuate manner to the alternate. operated positions.

7 9 Each selector bar, such as 50, supports a plurality of selection spring fingers such as 56, each of which fingers is located to cooperate with a corresponding pair of horizontal contact sets, such as 18, 2t 22, 24, in a vertical group such as 14. With the horizontal bar 50 in its normal position, each spring finger, such as 56*, lies between its two horizontal sets of contacts, such as 18, 20"; 22, 2-4 of its associated vertical group, such as 14.

With operation of the horizontal bar 50 from the nor-- mal position to one of the two operation positions, the flexible spring finger, such as 56, attached thereto is displaced up-wardly into position adjacent the U-shaped channel on contact actuating spring 42 or downwardly into position adjacent the U-shaped channel on contact actuating spring 44.

Terminal portions '68, 70 on horizontal contacts 18, 20 and terminal portions '64, 66 on vertical contacts 32,

' 34' may be used for connecting the crosspoints to external circuits Closure of the crosspoints is eifected by completin-g an operating circuit for the lower Winding 60 of 7 horizontal selected magnet H1 to effect attraction of armature 62 adjacent thereto, and the resultant tilting of the horizontal bar 50 upwardly to the position shown in FIGURE '1 to thereby move the spring-mounted selection fingers 56, 56A, etc., into spanning position relative to the U-shaped channels on the contact actuating springs, such as 42, 45 which are associated with such level of the horizontal contacts. With the operation of the vertical magnet 36 and the attraction of the armature 38 adjacent thereto, the vertical hold bar 40 presses against the selection linger 56 which spans the channel of spring 42 to cause the spring finger 56 and contact actuating spring 42 to move the ends of horizontal contacts 18, 2-3 into registration with the vertical contact strips 32, 34 to thereby close the crosspoints and complete a path from terminals 64, 66 to terminals 68, 70.

It will be apparent that as the horizontal magnet 6t operated to tilt the horizontal selection bar 50, a number of the spring fingers 56, 56A, etc., were placed in position adjacent their respective contact actuating spring such as 42. However, since a circuit is completed for only one of the vertical magnets '(36 in the present example) only the horizontal contacts 18, 20 which are in the vertical group 1 4 controlled by magnet 36 are closed.

After the connection is completed, the horizontal mag net 60 is d e-energized and selector bar is restored to its normal position to move the spring fingers, such as 56A, to the normal position between the two horizontal contact sets (not shown) associated therewith, and finger f 56 is held between vertical hold bar 40 and contact actuating spring 42. "It is apparent that the same horizontal magnets 58, 60 may now be used to complete connection over other crosspoints in the other vertical the contact actuating springs, such as 44, '46,.48 without effecting operation of the horizontal contacts associated therewith by reason of the fact that the spring fingers,

such as 56, were not moved across the channel of the contact actuating springs, such as 44, :to'gintercept the' vertical hold bar '40 'inits movement. I

Although the horizontal magnet, such as 60', which was used in the establishment of the connection, is now released for use in theestablishment of further calls over the other vertical contact units in the crossbar switch,

the vertical magnet 36 is maintained operated 'for the period that a connection is to be completed over contacts in the established path between terminals 64, 66; 68, 7h.

According to a-feature of the present invention, the novel crossbar switch includes vertical magnets such-as 36, which are of the magnetic latching type, such as shown in FIGURE 2. The latching relays there illustrated are operable, as energized, to operate the vertical hold bars, such as ill, to complete the desired one, of the transmission paths over the switch; are operable subsequent to the interruption of the energizing current to the relay to maintain the vertical hold bar 40 in its path completing posi tion; and are operable responsive to the momentary coupling of a current pulse of a given polarity thereto to release the vertical hold bar 40, and interrupt the path which extends over the contacts previously closed thereby.

As shown in FIGURE 2, the magnetic latching relay 36 basically comprises an l..-shaped pole piece72 having a first or shorter leg 74 extending perpendicular to a second or longer leg 76. A core member 78 having a threaded shank at one end thereof is secured to theshorter leg 74 by means including positioning means 80A, locknut 8i and screw means '81, the longitudinal axis of the core being disposed in parallel spaced relationwith the elongated pole piece leg '76 in such mounting. Positioning means 80A threading-1y engage the shorter leg 74 of the pole piece and are locked in a desired position by locknut 80. Screw means S l extend through the positioning means 80A and into the threaded shank of core member 78, whereby adjustment of the positioning means 80A and screw means 81 permits longitudinal adjustment of the core 78 for a purpose disclosed more full hereinafter.

An operating winding A, B, and a release winding C, D, are wound about core 78 in the manner shown in FIGURE 3, a wrapping of insulation 82 being wound about core 78 and insulation members 84, 84A being attached at either end of the core to form a spool-like portion upon which the coils A, B; C, D are readily wound. A wrapping 83v of suitable insulating material is wound about the outer periphery of the coil windings as completed.

Although the coils are shown as being wound in opposing directions, it will be appreciated that the coils may also be wound in the same direction and the polarity of the operating and release circuits applied to the terminals in a correspondingly different manner. Armature 38 is mounted for pivotal movement at 86 about a knife edge pivot formed at the one end of the leg 72, the armature being attracted by the magnetic path as established over core 78, air gap 88, armature 38, and pole piece 72 to core 78 whenever the operating coil A, B is energized momentarily by an electrical pulse of la. predetermined polarity and value.

Subsequent to movement of the armature 33 adjacent to andin contacting relation with core '78 and the termination of the pulse, the residual magnetism of the core extends over the path including core 78, armature 38 and pole piece 7-2 to maintain the armature 33 in the operated position. It is important that the armature 38 engage the end of core 78 with the faces of the two members as flat as possible, and positioning means 80, 80A and screw means 81 are provided to permit lateral adjustment of core 38 to accomplish such end.

As a release pulse of a predetermined value and the polarity indicated in. FIGURE 3 is coupled to release winding C, D, spring means associated with the load (and schematically shown as 91 in FIGURE 2) urge the armature 38 away from.the end of core 78, and hold bar 40 effects the opening of the contact set which was previously maintained closed thereby.

In the provision of a crossbar switch including a magnetic latching relay 36 which is capable of maintaining the contacts'of a crossbar switch in the operated position subsequent to interruption of the power thereto, it has been found that a special core material must be utilized to provide the necessary forces (a) for operating the armature reliably under load conditions which vary over a large range, (b) for holding the armature latched under such load for indeterminate periods of time even with the possible application of external forces to the crossbar switch or its support frame, and (c) for releasing the armature responsive to the momentary application of a pulse to the winding.

It has been discovered that a magnetic latching relay which is operable in crossbar switches used in telephone exchanges may be provided by using a material consisting of oil hardened clrill rod having a composition of carbon 95%, silicon- 30%, manganese 1.20%, tungsten- 50%, chromium 50%, vanadium-%, and hardening such material to a hardness of a minimum of 58 Rockwell C. The hardness of the material has been found to be directly related to the operating and latching characteristic of the core.

In one preferred embodiment the hardening process comprises the steps of heating the furnace to a value not in excess of 1300 F. After attaining furnace heat the cores are introduced and the temperature is advanced at such a rate that thin sections or small turnings will not heat more rapidly than thick sections. After the furnace has attained 1450 F. the work is soaked or held at such temperature for ten to twenty minutes before quenching in oil. The cores are then double tempered at 425 F. for one and one-half hours to provide a hardness of 58-60 Rockwell C.

It was discovered that the physical hardness produced by such heat treatment was related to the magnetic latching properties of the device, and that by hardening the high carbon steel to a 58-60 Rockwell C it is possible to produce a core for a magnetic latching relay which has the proper operating characteristics for successful use as a vertical magnet in a crossbar switch which not uncom OPERATING WINDIN G Turns Wire Size Resistance 50 v.D.G.

34 149 milliamperes.

1,190 ampereturns.

RELEASE WINDING 40 900 53 milliampsres. 8 ampereturns.

In such arrangements under severe combinations of loads and conditions, it was found that the crossbar switch magnets operated successfully with an average operate pulse of 27 milli-seconds to hold and an approximately 6 milli-seconds pulse to release.

The use of the novel crossbar switch including the magnetic latching relays having the core material of the disclosure are capable of providing automatic telephone exchanges and data switching networks which are capable of providing reliable switching with a minimum of power. Further, the nature of the novel crossbar switch is such that the construction used to provide the desired results does not incorporate any mechanical latches or critical circuitry which would entail additional maintenance problems or expense. As a result, large savings in the cost of exchange operation are effected, and anincreased use and application of crossbar switching equipment is made possible in locations where available power is a problem.

Although only a particular embodiment of the invention has been shown and described, it is apparent that modifications and alterations may be made therein, and

modifications and alterations as may fall within the true spirit and scope of the invention.

What is claimed is: g

'1. A mechanical crossbar switch comprising at least one set of horizontal contacts and at least one set of vertical contacts supported in spaced aligned relation with each other, selector means supported adjacent said contact sets for completing a circuit connection over said contact sets, a magnetic latching magnet support-ed on said switch comprising at least one winding on a core consisting of high carbon steel material having a hardness in the range of at least 5 8 Rockwell C and an armature member supported for movement adjacent tosaid core responsive to energization of said winding, the residual magnetisrn provided by said core subsequent to removal of the energizing force retaining the armature in such position, and operating means connected to said armature member operative responsive to energization of said magnet winding to operate said selector means in the completion of a circuit over said horizontal and vertical contact sets.

2. A mechanical crossbar switch comprising at least one set of horizontal contacts and at least one set of vertical contacts supported in spaced aligned relation with each other, selector means supported adjacent said contact sets for completing a circuit connection over said contact sets, a magnetic latching magnet supported on said switch comprising at least one winding on a core consisting of high carbon steel material in the order of 1% carbon and having a hardness in the range of 58-60 Rockwell C and an armature member supported for movement adjacent to said core responsive to energization of said winding, the residual magnetism provided by said core sub sequent to removal of the energizing force retaining the armature in such position, and operating means connected to said armature member operative responsive to energization of said magnet winding to operate said selector means in the completion of a circuit over said horizontal and vertical contact sets.

3. A mechanical crossbar switch comprising at least one set of horizontal contacts and at least one set of vertical contacts supported in spaced aligned relation with each other, selector means supported adjacent said contact sets to control the extension of circuit paths thereover, a magnetic'latching magnet supported on said switch having at least one winding on a core consisting of high carbon steel material comprised of .95% carbon, 30% silicon, 1.20% manganese, .50% tungsten, 50% chromium, and 20% vanadium, said core having a hardness in the range of 58-60 Rockwell C and an armature member supported for movement adjacent to said core responsive to energization of said winding, the residual magnetism provided by said core subsequent to removal of the "energizing force retaining the armature in such position, and operating means connected to said armature operative responsive to energization of said magnet to operate said selector means in the completion of a circuit over said horizontal and vertical contact sets.

4. A mechanical crossbar switch for use in an automatic telephone exchange comprising at least one set of horizontal contacts and at least one set of vertical contacts supported in spaced aligned relation with each other, selector means supported adjacent said contact sets for controlling said contact sets in the completion of circuit paths thereover, a magnetic latching magnet supported on said switch including a first anda second winding wound on a core consisting of high carbon steel material having a hardness in the range of 58-60 Rockwell C, said first winding having a number of turns sufficient as energized to provide in the order of 1190 ampere turns and said second winding having a number of turns sulficient to provide in the order of 188 ampere turns for release purposes responsive to the energization thereof, and an armature member supported for movement adjacent to said core responsive to energization of said first winding, the residual magnetism provided by the core subsequent to the removal of the energizing force retaining the armature in such position and operating means connectedto said armature member operative responsive to energization of said first winding on said magnet to operate said selector means in the completion of a circuit over said horizontal and vertical contact sets and operative responsive to energization of said second winding on said magnet to interrupt said circuit. I

5. An electromagnetic relay device for use in a crossbar switch for an automatic telephone exchange comprised of at least one winding on a core consisting of high carbon steel material having .95,% carbon, 30% silicon, 1.20% manganese, tungsten, 50% chromium and 20% vanadium, and having'a hardness in therange of 58-60 Rockewll C, terminal means for coupling an energizing potential to said winding, and an armature member operatively controlled responsive to energization of saidmagnet coil to move to atposition adjacent one end of said core for retention by the residual magnetism of the core subsequent to termination of the coupling of the energizing potential to said magnet coil.

References Qited in the file of this patent I UNITED STATES PATENTS 2,114,046 Burwell Apr. 12, 1938 2,187,115 Ellwood et a1. Jan. 16, 1940 2,260,810 Jones Oct. 28,1941 2,802,078 Martin Aug. 6, 1957 2,877,315 Oliver Mar. 10, 1959 

1. A MECHANICAL CROSSBAR SWITCH COMPRISING AT LEAST ONE SET OF HORIZONTAL CONTACTS AND AT LEAST ONE SET OF VERTICAL CONTACTS SUPPORTED IN SPACED ALIGNED RELATION WITH EACH OTHER, SELECTOR MEANS SUPPORTED ADJACENT SAID CONTACT SETS FOR COMPLETING A CIRCUIT CONNECTION OVER SAID CONTACT SETS, A MAGNETIC LATCHING MAGNET SUPPORTED ON SAID SWITCH COMPRISING AT LEAST ONE WINDING ON A CORE CONSISTING OF HIGH CARBON STEEL MATERIAL HAVING A HARDNESS IN THE RANGE OF AT LEAST 58 ROCKWELL "C" AND AN ARMATURE MEMBER SUPPORTED FOR MOVEMENT ADJACENT TO SAID CORE RESPONSIVE TO ENERGIZATION OF SAID WINDING, THE RESIDUAL MAGNETISM PROVIDED BY SAID CORE SUBSEQUENT TO REMOVAL OF THE ENERGIZING FORCE RETAINING THE ARMATURE IN SUCH POSITION, AND OPERATING MEANS CONNECTED TO SAID ARMATURE MEMBER OPERATIVE RESPONSIVE TO ENERGIZATION OF SAID MAGNET WINDING TO OPERATE SAID SELECTOR MEANS IN THE COMPLETION OF A CIRCUIT OVER SAID HORIZONTAL AND VERTICAL CONTACT SETS. 